The present invention is directed to an Environmental Control System featuring an advanced semiclosed reverse Brayton air cycle loop with a unique air cycle machine. The air cycle machine includes dual turbines drivingly coupled to a compressor. Within the air cycle machine, one of the turbines is coupled to directly receive engine bleed air and extract useful work therefrom. The resulting Environmental Control system (ECS) minimizes the amount of bleed air required from the main engines, reducing the amount by up to 60 percent over present air cycle ECS systems.
Environmental Control Systems (ECS's) are in widespread use to provide a supply of conditioned air to an enclosed space, as for example an aircraft cabin and cockpit. Presently, the most efficient ECS's operate on a flow of bleed air taken from an intermediate or high pressure stage within a jet engine having multi-compression stages. The bleed air is first precooled within a primary heat exchanger, dumping heat to ram air, and is then ducted to a compressor. After compression, the air is routed through a series of heat exchangers and condensors, then expanded through a turbine before being ducted to the cabin. The turbine is mechanically linked to drive the compressor. These systems also incorporate various bypass lines, valves and controller means to regulate the temperature of the air delivered to the cabin.
Modern high performance aircraft also require cooling for aircraft avionics. This added cooling load may exceed the cooling load requirement of the cockpit and cabin. As a practical consideration, the avionics are preferably cooled by a liquid cooling cycle. Thus, various dual air-liquid cooling systems have been explored to provide the required cooling for the aircraft.